Given a CLIST (which is intended to run under TSO batch TMP like IKJEFT01) that issues ISPSTART or equivalent command to start ISPF in the TSO/BATCH address space, could it be run in foreground by BC1PTMP0 processor utility?

Answer:

That is not possible because, when the CLIST is executed in a foreground processor, ISPF is already active in the address space and any subsequent invocation of commands like ISPSTART will fail with a message like: